title: A web search on environmental topics: what is the role of ranking?
abstract: BACKGROUND
  Although the Internet is easy to use, the mechanisms and logic behind a Web search are often unknown. Reliable information can be obtained, but it may not be visible as the Web site is not located in the first positions of search results. The possible risks of adverse health effects arising from environmental hazards are issues of increasing public interest, and therefore the information about these risks, particularly on topics for which there is no scientific evidence, is very crucial. The aim of this study was to investigate whether the presentation of information on some environmental health topics differed among various search engines, assuming that the most reliable information should come from institutional Web sites.
  
  
  METHODS
  Five search engines were used: Google, Yahoo!, Bing, Ask, and AOL. The following topics were searched in combination with the word "health": "nuclear energy," "electromagnetic waves," "air pollution," "waste," and "radon." For each topic three key words were used. The first 30 search results for each query were considered. The ranking variability among the search engines and the type of search results were analyzed for each topic and for each key word. The ranking of institutional Web sites was given particular consideration.
  
  
  RESULTS
  Variable results were obtained when surfing the Internet on different environmental health topics. Multivariate logistic regression analysis showed that, when searching for radon and air pollution topics, it is more likely to find institutional Web sites in the first 10 positions compared with nuclear power (odds ratio=3.4, 95% confidence interval 2.1-5.4 and odds ratio=2.9, 95% confidence interval 1.8-4.7, respectively) and also when using Google compared with Bing (odds ratio=3.1, 95% confidence interval 1.9-5.1).
  
  
  CONCLUSIONS
  The increasing use of online information could play an important role in forming opinions. Web users should become more aware of the importance of finding reliable information, and health institutions should be able to make that information more visible.
authors.affiliation: 1 Department of Medical and Surgical Specialties, Radiological Sciences, and Public Health, University of Brescia , Brescia, Italy .
authors.forename: Loredana
authors.initials: L
authors.lastname: Covolo
authors.forename: Barbara
authors.initials: B
authors.lastname: Filisetti
authors.forename: Silvia
authors.initials: S
authors.lastname: Mascaretti
authors.forename: Rosa Maria
authors.initials: RM
authors.lastname: Limina
authors.forename: Umberto
authors.initials: U
authors.lastname: Gelatti
mesh_terms: D015706:Bibliometrics; D016001:Confidence Intervals; D004782:Environmental Health; D016247:Information Storage and Retrieval; D016017:Odds Ratio; D057386:Search Engine